1. Field of the Invention
The present invention relates to an air conditioning apparatus having a dehumidifying operation function for removing moisture in the indoor air.
2. Description of the Related Art
An air conditioning apparatus is known which is equipped with two indoor heat exchangers and an electric expansion valve through which these indoor heat exchangers are connected.
In this air conditioning apparatus, when the electric expansion valve is fully opened no pressure-reducing action is exerted on a refrigerant flowing between the indoor heat exchangers and, under this action, the respective indoor heat exchangers serves as one heat exchanger. When the extent of opening of the electric expansion valve is reduced a pressure-reducing action is exerted on the refrigerant flowing between the indoor heat exchangers and the respective indoor heat exchangers act as mutually different heat exchangers.
If, for example, the respective indoor heat exchangers are made to function both as evaporators with the electric expansion valve fully opened, it is possible to perform a cooling operation. If, on the other hand, the respective indoor heat exchangers are made to function both as condensers with the electric expansion valve fully opened, it is possible to perform a heating operation.
If, with the extent of opening of the electric expansion valve reduced, one of these indoor heat exchangers is made to function as the condenser (reheater) and the other indoor heat exchanger as the evaporator, then it is possible to perform a dehumidifying operation. Put it in another way, indoor air is cooled and dehumidified through the evaporator and, thereafter, reheated and blown into a room.
The air conditioning apparatus equipped with such a dehumidifying operation function is disclosed, for example, in Published Examined Japanese Patent Application No. 61-43631, Published Unexamined Japanese Patent Application Nos. 3-164666, 3-177755, 3-255861 and 2-203172 and Published Examined Japanese Utility Model Registration Application No. 62-40289.
At the dehumidifying operation time, an outdoor heat exchanger functions as a condenser. In cases where an amount of refrigerant heat released varies in the outdoor heat exchanger it is possible to control the air blown into the room, that is, the temperature in the dehumidified air.
In cases where the flow of the outdoor air into the outdoor heat exchanger is stopped with an outdoor fan OFF, the amount of refrigerant heat released is decreased in the outdoor heat exchanger. With a decrease the amount of refrigerant heat released, the temperature of the dehumidified air rises so that a dehumidifying operation is carried out on a somewhat "heating" side.
With the outdoor fan ON and its speed increased, more refrigerant heat is released in the outdoor heat exchanger. With an increase in the refrigerant heat released, the temperature of the dehumidified air is lowered and the dehumidifying operation is carried out on a somewhat "cooling" side.
In the dehumidifying operation with the outdoor fan kept ON, the liquefying of the refrigerant is stable in the outdoor heat exchanger in which case a liquid-phase refrigerant passes through the electric expansion valve between the respective indoor heat exchangers.
With the outdoor fan changed from an ON to an OFF state, on the other hand, the liquefying of the refrigerant becomes temporarily unstable in the outdoor heat exchanger in which case a gas-mixed refrigerant under a pressure ripple flows toward an indoor side and across the electric expansion valve. At that time, noise occurs upon mixing together of the liquid and gas refrigerants, thus imparting disturbing noise to an occupant or occupants in the room.
Even with the outdoor fan changed from an OFF to an ON state a similar phenomenon occurs, thus imparting a feeling of discomfort to the occupant in the room.
Even when a dehumidifying mode is used at a start of operation of the apparatus, the liquefying of the refrigerant becomes unstable in the outdoor heat exchanger so that a gas-mixed liquid refrigerant under a rippling pressure passes through the electric expansion valve at which time disturbing noise is produced.